Processes involved in cognitive re-adjustment to rapidly changing task demands will be examined. These processes are termed "cognitive dynamics." Principal questions concern the impact of varying task characteristics upon human information processing in general, performance limitations associated with changing task demands, and the time and/or processing capacity requirements of cognitive re-adjustment. Subsidiary research concerning attention, speed-accuracy tradeoff, and double-stimulation will be conducted. In one phase of the project speed vs. accuracy demands of a double-stimulation choice-reaction task will shift between the first and second of two sequential decision components. The first-response-to-second-stimulus interval (RSI) will be varied to allow differential time for cognitive re-adjustment. In the second phase, stimulus-response mapping rules will be varied in a similar fashion.